共查询到19条相似文献,搜索用时 146 毫秒
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1实验系统本文选定花瓣形翅片管作为强化管型,并探讨非共沸混合工质在其管束上的冷凝传热性能。实验系统如图1所示。本实验系统设计成既可进行大空间内的自然对流冷凝传热实验研究,又可进行套管空间内的强制对流冷凝传热研究。实验工质民;和R;。在蒸气发生器中由电加热器加热沸腾后所产生的蒸气分两路进入冷凝器空间内,并在管束上冷凝。实验管(管参数如表1所示)内的冷却水来自调温水箱,实验时控制三条管内水流量基本上相同。对于大空间内的自然对流,分别研究了光管和花瓣形翅片管管束直列与错列下的冷凝传热性能对比。对于套管空… 相似文献
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翅片管传热特性与热疲劳的实验研究 总被引:1,自引:0,他引:1
通过实验,对U形翅片管和高频焊翅片管的传热性能及接触热阻作了对比性研究。并对U形翅片管的热疲劳特性进行了实验。结果表明,U形翅片管具有较好的传热性能和抗疲劳性 相似文献
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强制对流冷凝传热强化 总被引:1,自引:0,他引:1
研究了强制对流条件下,非共沸混合工质R11/R113在三排水平直列光滑管及花瓣形翅片管束外的冷凝传热。实验结果表明:花瓣形翅片管由于具有特殊的三维翅片结构,既能激发流动的蒸气产生强烈地湍流,减小其气膜热阻,又能充分发挥冷凝液表面张力的作用,减少其液膜热阻,从而显著地强化了非共沸混合工质在管束外的冷凝传热。在相同热流率下,其管束平均冷凝传热系数是光滑管管束的3~5倍。 相似文献
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Turbulators are applied to increase the thermal efficiency of heat transfer units. The additional pressure drop can be challenging for the self-circulation of thermosiphon reboilers. Thus, the effects of hiTRAN®-wire matrix inserts for the boiling of water and a water/glycerol mixture were investigated herein, using the performance of a thermosiphon reboiler with plain tubes as a reference. The reboiler was operated at sub-atmospheric pressures, small driving temperature differences, and under flooded conditions. Favorable and unfavorable operating conditions for using inserts were specified. Especially for the water/glycerol mixture, significant improvements of self-circulation and heat transfer up to six times compared to the plain tube reference were observed, allowing an operation of thermosiphon reboilers at smaller driving temperature differences under sub-atmospheric pressures. 相似文献
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The experiments of pool boiling were carried out on the T-shaped finned surfaces. The produced surfaces have precise geometric sizes. Therefore, the analysis of the heat transfer mechanism and the research of the optimal structural size are easily conducted. Based on the experiments and observations, a countercurrent two-phase flow model for boiling heat transfer on the T-shaped finned surfaces was proposed. Both relation for the heat transfer and the relation for the optimal slit width between T-shaped fins were obtained. The model was further extended to Thermoexcel-E surfaces, yielding the corresponding heat transfer relation. 相似文献
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轴向挤压式胀管法能使管子在特定的条件下有效地控制变形量和胀管率,应用此法修复的再沸器,其胀管率和拉脱力均符合要求,产品修复出厂后得到用户的好评。 相似文献
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环保工质与高效冷凝管的应用对制冷行业实现节能减排意义重大,工质在强化管外膜状凝结换热特性是二者推广应用的关键。建立了水平管外膜状凝结换热试验系统,研究了HFC134a在4种二维肋管与2种三维肋管外的膜状凝结传热特性。试验管公称外径为19.05 mm、有效换热长度为1000 mm;试验中,通过改进的Wilson图解法获取试验管水侧对流传热系数。结果表明: HFC134a水平二维与三维肋管外冷凝传热系数分别达到同热通量下光管的11倍与19倍以上;HFC134a工质对应最佳二维肋管的肋密度在1069~1575fpm(肋每米)之间、肋高在0.7~1.5 mm之间,对应最优三维肋管(与本文试验肋型相似)肋密度低于2000fpm;既有二维肋管膜状凝结换热模型需要进一步完善,肋管结构优化过程中应遵循优先提升肋密度的原则。 相似文献
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In this paper, the standard k-εtwo-equation model is adopted to numerically simulate fully developed fluid flow and heat transfer in a spiral finned tube within a cracking furnace for ethylene manufacturing. By variable transformation, the orlglnal 3-D problem is converted into a 2-D problem in spiral coordinates. The algorithm of SIMPLEC is used to study the fully developed fluld flow and heat transfer in the spiral finned tube at constant periphery temperature and constant axial heat flux, The computed results agree pretty well with the experimental data obtained from the industry, Further studies on the fluid flows and temperature profiles at different Reynolds numbers within straight and spiral finned tubes are conducted and the mechanisms involved are explored. It is found that with the spiral finned tube, pressure drop increases to a great extent whereas heat transfer tends to be decreased. 相似文献
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通过热力学第一、第二定律,对管内对流换热综合性能进行熵产分析和评价.建立了一种基于流动与传热过程熵增原理的统一分析方法,在等壁温边界条件下进行熵产分析.并以文献中内翅片管的强化传热作为应用,分别对相同流量、泵功、压降在等热负荷限制下进行强化传热性能评价.结果表明:对于给定的管道,量纲1熵产数只与流动Reynolds数和进口与壁面的温度差有关.利用该分析方法不仅可通过参数分析获得几种强化方式的能量综合利用效果,还可确定合理的流动工况参数、结构参数和合理的强化形式. 相似文献
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热管是一种利用工质相变传热,具有传热温差小、热响应速度快、换热量大等优点的传热元件。为研究翅片重力热管的传热性能,实验测试了翅片重力热管与平板重力热管(铝-丙酮工质)的传热性能,比较了其瞬态热响应速率,获得了翅片与平板重力热管在蒸发段不同电功率稳定加热条件下表面温度沿高度方向的变化规律,计算了平板热管的等效热导率,并与铝板测量结果进行了对比。结果表明:重力热管传热速度快、表面均温效果好,热导率随功率的增大先升高后降低,整体上热导率高达纯铝的84~258倍,翅片热管相比于平板热管具有更好的均温性和散热效果,在建筑供暖、车载电池散热、余热利用等领域具有广泛的应用前景。 相似文献